-
Notifications
You must be signed in to change notification settings - Fork 0
/
simulation.c
241 lines (209 loc) · 4.66 KB
/
simulation.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <math.h>
#include <time.h>
#include "config.h"
/*
* A cache simulation:
*
* Array (2^n) of lines that contain blocks (2^n) - offsets
* Blocks that contain multiple cached values (tag, value) - indexes
*
* Prefetcher (on new read or write)
* Cache policy (replacing value when no place to add tag)
* Associativity
*
* Example:
*
* Mem 1024B
* Block 128B
* Assoc 4
*
* Indexes:
* That gives 2 indexes = Mem/(block*assoc), nb bits (log(2)/log(2) = 1 bit
* [ 4 first blocks index 1][ 4 others blocks index 2]
*
* Offset:
* block 128B -> log(128)/log(2) = 7 bits
* 0x123456789ABCDEF
* 0b1001000110100010101100111100010011010101111001101 1 1101111
* offset = 1101111
* index = 1
* tag = 1001000110100010101100111100010011010101111001101
* whatever the offset if the index is the same and tag the same then
* it's the same address block
*
* Tag can be compared with XNOR
*
* References:
* https://people.freebsd.org/~lstewart/articles/cpumemory.pdf
* https://en.wikipedia.org/wiki/Cache_(computing)
* http://csillustrated.berkeley.edu/PDFs/handouts/cache-3-associativity-handout.pdf
* https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/Memory/fully.html
* https://stackoverflow.com/questions/30097648/difference-between-a-direct-mapped-cache-and-fully-associative-cache
* https://github.com/auxiliary/CacheSimulator
*/
struct line {
unsigned long index;
unsigned long offset;
unsigned long tag;
time_t last_access;
char buff[BLOCKS_SIZE];
};
typedef struct line* blocks;
typedef blocks* cache;
struct action {
char rw;
unsigned long address;
};
void
help(char *argv)
{
printf("usage: %s <mem_file>\n", argv);
}
/*
* Read a text file with some addresses and actions:
*
* R: 0x<address>
* W: 0x<address>
*/
struct action*
read_action_from_file(char *file_name)
{
FILE *f;
char rw;
unsigned long address;
struct action *actions;
unsigned int nb_actions;
unsigned int current_action;
f = fopen(file_name, "r");
if (f == NULL) {
perror(NULL);
exit(1);
}
nb_actions = 40;
actions = malloc(sizeof(struct action) * nb_actions);
current_action = 0;
while (fscanf(f, " %c: 0x%12x", &rw, &address) != EOF) {
if (current_action + 2 > nb_actions) {
nb_actions += 40;
actions = realloc(actions, sizeof(struct action) * nb_actions);
}
actions[current_action].rw = rw;
actions[current_action].address = address;
current_action++;
}
// use this as the delimiter
actions[current_action].rw = '\0';
fclose(f);
return actions;
}
struct line
line_from_address(unsigned long address)
{
struct line l;
l.offset = address & ((1 << BLOCKS_SIZE_N) - 1);
l.index = (address >> BLOCKS_SIZE_N) & ((1 << NB_BLOCKS_N) - 1);
l.tag = (address >> (BLOCKS_SIZE_N+NB_BLOCKS_N));
l.last_access = time(NULL);
//printf("line info: offset: %4x, index: %4x, tag: %10x\n",
// l.offset, l.index, l.tag);
return l;
}
char
in_cache(cache c, struct line l)
{
unsigned int i;
for (i = 0; i < ASSOCIATIVITY; i++) {
// could be xnor
if (c[l.index][i].tag == l.tag) {
return 1;
}
}
return 0;
}
void
add_to_cache(cache c, struct line l)
{
unsigned int i, oldest;
time_t oldest_time;
oldest_time = time(NULL);
for (i = 0; i < ASSOCIATIVITY; i++) {
// found an empty line then use it
if (c[l.index][i].tag == 0x00) {
c[l.index][i] = l;
return;
} else {
if (c[l.index][i].last_access < oldest_time) {
oldest_time = c[l.index][i].last_access;
oldest = i;
}
}
}
// there's no space left in the group
// what do we do?
// swap the oldest one by this one
c[l.index][oldest] = l;
}
void
execute_mem(struct action *actions)
{
cache c;
unsigned int i;
struct line l;
unsigned int hits;
unsigned int misses;
hits = misses = 0;
c = malloc(sizeof(blocks) * NB_BLOCKS);
if (c == NULL) {
perror(NULL);
exit(1);
}
for (i = 0; i < NB_BLOCKS; i++) {
c[i] = calloc(ASSOCIATIVITY, sizeof(struct line));
if (c[i] == NULL) {
perror(NULL);
exit(1);
}
}
for (i = 0; actions[i].rw != '\0'; i++) {
l = line_from_address(actions[i].address);
if (in_cache(c, l)) {
hits++;
} else {
add_to_cache(c,l);
if (PREFETCHING) {
l = line_from_address(actions[i].address+BLOCKS_SIZE);
if (!in_cache(c, l)) {
add_to_cache(c, l);
misses++;
}
}
misses++;
}
}
printf("Hits: %d, Misses: %d\n", hits, misses);
// cleanup
for (i = 0; i < NB_BLOCKS; i++) {
free(c[i]);
}
free(c);
}
int
main(int argc, char **argv)
{
struct action *actions;
if (argc < 2) {
help(argv[0]);
exit(1);
}
actions = read_action_from_file(argv[1]);
execute_mem(actions);
if (actions != NULL) {
free(actions);
}
return 0;
}